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Chaparro J.A.,Escuela Colombiana de Ingenieria | Giraldo B.F.,CIBER ISCIII
2014 36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC 2014 | Year: 2014

Disconnection from mechanical ventilation, called the weaning process, is an additional difficulty in the management of patients in intensive care units (ICU). Unnecessary delays in the discontinuation process and a weaning trial that is undertaken too early are undesirable. In this study, we propose an extubation index based on the power of the respiratory flow signal (Pi). A total of 132 patients on weaning trials were studied: 94 patients with successful trials (group S) and 38 patients who failed to maintain spontaneous breathing and were reconnected (group F). The respiratory flow signals were processed considering the following three stages: a) zero crossing detection of the inspiratory phase, b) inflection point detection of the flow curve during the inspiratory phase, and c) calculation of the signal power on the time instant indicated by the inflection point. The zero crossing detection was performed using an algorithm based on thresholds. The inflection points were marked considering the zero crossing of the second derivative. Finally, the inspiratory power was calculated from the energy contained over the finite time interval (between the instant of zero crossing and the inflection point). The performance of this parameter was evaluated using the following classifiers: logistic regression, linear discriminant analysis, the classification and regression tree, Naive Bayes, and the support vector machine. The best results were obtained using the Bayesian classifier, which had an accuracy, sensitivity and specificity of 87%, 90% and 81% respectively. © 2014 IEEE.


Castellanos N.T.,Escuela Colombiana de Ingenieria | Agredo J.T.,National University of Colombia | De Gutierrez R.M.,University of Valle
ACI Materials Journal | Year: 2016

In this paper, the mechanical properties of concrete with an added residue of the petrochemical industry (at levels of 10, 20, 30%), called catalytic cracking catalyst residue (FCC), are evaluated. The mechanical properties evaluated include compressive strength, modulus of elasticity, flexural strength, and ultrasonic pulse velocity. Two reference materials, portland cement concrete without addition and added with 20% of metakaolin (MK), were used. These tests were performed up to 360 days of curing age. Based on the results obtained, correlations were established between the different properties evaluated. The best mechanical performance was obtained with 10% FCC as a cement replacement. © Copyright 2016, American Concrete Institute. All rights reserved.


Chaparro J.A.,Escuela Colombiana de Ingenieria
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2011

One of the most challenging problems in intensive care is the process of discontinuing mechanical ventilation, called weaning process. An unnecessary delay in the discontinuation process and an early weaning trial are undesirable. This paper proposes to analysis the respiratory pattern variability of these patients using autoregressive modeling techniques: autoregressive models (AR), autoregressive moving average models (ARMA), and autoregressive models with exogenous input (ARX). A total of 153 patients on weaning trials from mechanical ventilation were analyzed: 94 patients with successful weaning (group S); 38 patients that failed to maintain spontaneous breathing (group F), and 21 patients who had successful weaning trials, but required reintubation in less than 48 h (group R). The respiratory pattern was characterized by their time series. The results show that significant differences were obtained with parameters as model order and first coefficient of AR model, and final prediction error by ARMA model. An accuracy of 86% (84% sensitivity and 86% specificity) has been obtained when using order model and first coefficient of AR model, and mean of breathing duration.


Torres Castellanos N.,Escuela Colombiana de Ingenieria | Torres Agredo J.,National University of Colombia | Mejia de Gutierrez R.,University of Valle
Ingenieria e Investigacion | Year: 2013

In this work the evaluation of the performance of concrete added with Fluid Catalytic Cracking Catalyst residue (FCC) from a Colombian petroleum company, under sulfate attack, is presented. The results of this concrete are compared with the results of Me-takaolin (MK) added concrete. The analysis of the pozzolanic materials included the determination of the particle size, the poz-zolanic activity and the chemical and mineralogical composition. Different percentages of FCC were used as Portland cement replacement in proportions of 0, 10, 20 and 30%; similarly concrete added with 20% of MK as replacement was elaborated. Com-pressive strength and performance under sulfate attack were evaluated. Results showed that concrete with FCC and MK as well as control concrete had similar behavior; however its expansion was higher. In addition, the performance of the two types of concrete (FCC y MK) under sulfate attack was comparable; this could be due to fact that FCC and MK showed similarities regarding of their chemical and mineralogical composition. Importantly, after 360 days of exposure the specimens with MK and FCC showed no significant deterioration.


Archilla A.R.,University of Hawaii at Manoa | Diaz L.G.,Escuela Colombiana de Ingenieria
Transportation Research Record | Year: 2011

The hot-mix asphalt (HMA) rutting prediction model in the Mechanistic-Empirical Pavement Design Guide (MEPDG) uses a relationship that includes the effects of mix characteristics only through the resilient strain, which in turn is a function of the dynamic modulus (|E*|) of the mix. However, increasing evidence suggests that the use of |E*| alone may be insufficient to characterize completely the permanent deformation behavior of HMA. In addition to effects already considered by the MEPDG model with |E*|, the effects of mix characteristics on permanent deformation are analyzed with the use of the results of repetitive axial permanent deformation tests from laboratory-compacted HMA specimens. Results of multiple linear regression analysis indicate that binder type, effective binder content, and air void content have significant effects on model parameters for permanent deformation. The potential effects of mix characteristics on these parameters are analyzed with the use of the MEPDG model and an HMA pavement section with four levels of compaction. Scenarios in which the mixture characteristics are incorporated solely by means of |E*| are compared with scenarios in which the effects of air void content and asphalt content are incorporated into the rutting prediction model by adjusting its parameters according to relationships established in the laboratory. Empirical laboratory evidence supports the hypotheses that, regardless of mixture properties, universal values for permanent deformation model parameters do not fully account for mixture-specific contributions to rutting and that other mix characteristics (e.g., air void content) may be needed to supplement |E*| for the appropriate characterization of the permanent deformation of asphalt mixtures.


Ladino L.A.,Escuela Colombiana de Ingenieria
Physics Education | Year: 2013

A different method to study the charging and discharging processes of a capacitor is presented. The method only requires a high impedance voltmeter. © 2013 IOP Publishing Ltd.


Acosta M.A.C.,Escuela Colombiana de Ingenieria | Rengifo H.F.C.,Escuela Colombiana de Ingenieria
2015 10th Colombian Computing Conference, 10CCC 2015 | Year: 2015

Given the serious impact that cardiovascular diseases are having in Colombia's deaths, the Colombian School of Engineering has been developing a platform for remote, real time, cardiac signals processing. One of the main challenges of this type of platform, assuming a relatively large population continuously transmitting their signals, is to guarantee good response times for all system's stakeholders (doctors, family, etc.), which is not always possible with the application models that have been traditionally used to build most of services that reside on the Web. This article describes an alternative software architecture proposed for the backend of such telemedicine system, which considers the non-blocking and actor-based programming models, as an alternative to the multi-thread model, and as a mean to simplify such system's scalability. © 2015 IEEE.


Rocha C.,Escuela Colombiana de Ingenieria
2013 8th Computing Colombian Conference, 8CCC 2013 | Year: 2013

The Invariant Analyzer Tool is an interactive tool that mechanizes an inference system for proving safety properties of concurrent systems, which may be infinite-state or whose set of initial states may be infinite. This paper presents the automatic proof-search heuristics at the core of the Maude Invariant Analyzer Tool, which provide a substantial degree of automation and can automatically discharge many proof obligations without user intervention. These heuristics can take advantage of equationally defined equality predicates and include rewriting, narrowing, and SMT-based proof-search techniques. © 2013 IEEE.


Rocha C.,Escuela Colombiana de Ingenieria
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

The logic of E.W. Dijkstra and C.S. Scholten has been shown to be useful in program correctness proofs and has attracted a substantial following in research, teaching, and programming. However, there is confusion regarding this logic to the point in which, for some time, it was not considered a logic, as logicians use the word. The main objections arise from the fact that: (i) symbolic manipulations seem to be based on the meaning of the terms involved, and (ii) some notation and the proof style of the logic are different, to some extent, from those found in the traditional use of logic. This paper presents the Dijkstra-Scholten logic as a formal system, and explains its proof-theoretic foundations as a formal system, thus avoiding any confusion regarding term manipulation, notation, and proof style. The formal system is shown to be sound and complete, mainly, by using rewriting and narrowing based decision and semi-decision procedures for, respectively, propositional and first-order logic previously developed by C. Rocha and J. Meseguer. © Springer International Publishing Switzerland 2015.


Chaparro J.A.,Escuela Colombiana de Ingenieria
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2012

Weaning trials process of patients in intensive care units is a complex clinical procedure. 153 patients under extubation process (T-tube test) were studied: 94 patients with successful trials (group S), 38 patients who failed to maintain spontaneous breathing and were reconnected (group F), and 21 patients with successful test but that had to be reintubated before 48 hours (group R). The respiratory pattern of each patient was characterized through the following time series: inspiratory time (T(I)), expiratory time (T(E)), breathing cycle duration (T(Tot)), tidal volume (V(T)), inspiratory fraction (T(I)/T(Tot)), half inspired flow (V(T)/T(I)), and rapid shallow index (f/V(T)), where f is respiratory rate. Using techniques as autoregressive models (AR), autoregressive moving average models (ARMA) and autoregressive models with exogenous input (ARX), the most relevant parameters of the respiratory pattern were obtained. We proposed the evaluation of these parameters using classifiers as logistic regression (LR), linear discriminant analysis (LDA), support vector machines (SVM) and classification and regression tree (CART) to discriminate between patients from groups S, F and R. An accuracy of 93% (98% sensitivity and 82% specificity) has been obtained using CART classification.

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